Heat exchangers

ABSTRACT

The heat exchanger comprises a bank of substantially straight and parallel tubes surrounded by a shell, the bank being constituted by juxtaposing adjacent layers of tubes, each layer extending between its own inlet and outlet manifolds. With such an arrangement, it is easy to provide a tube bank where the tubes lay in line with one another when the bank is viewed from above or from one side and this does not give optimum heat transfer between fluids within the tubes and fluids passed across the tubes in the tube bank. According to the present invention, the adjacent tubes in each layer are deflected by springing from near their ends so that alternate tubes in one layer are deflected in opposite ways and adjacent tubes in adjacent layers are deflected in the same way, to give better heat transfer efficiency.

United States Patent [22] Filed [45] Patented [73] Assignee Apr. 15, 1969 June 1, 1971 Foster Wheeler John Brown Boilers Limited London, England [32] Priority Apr. 16,1968 [33] Great Britain [31 18001/68 [54] HEAT EXCHANGERS 2 Claims, 5 Drawing Figs.

[56] References Cited UNITED STATES PATENTS 3.112.793 12/1963 Sass Primary Examiner-Charles Sukalo AttorneyDowell & Dowell ABSTRACT: The heat exchanger comprises a bank of substantially straight and parallel tubes surrounded by a shell, the bank being constituted by juxtaposing adjacent layers of tubes, each layer extending between its own inlet and outlet manifolds. With such an arrangement, it is easy to provide a tube bank where the tubes lay in line with one another when the bank is viewed from above or from one side and this does not give optimum heat transfer between fluids within the tubes and fluids passed across the tubes in the tube bank. According to the present invention, the adjacent tubes in each layer are deflected by springing from near their ends so that alternate tubes in one layer are deflected in opposite ways and adjacent tubes in adjacent layers are deflected in the same way, to give better heat transfer efficiency.

, PATENTED Jun H I 51 4 1 SHEET 1 0F 2 Heat exchangers of the so-called manifold type comprise a tube bank surrounded by a shell and at their ends the tubes in the tube bank are connected to a number of manifolds. The connection between the tubes and manifolds is such that all the tubes in a layer or sheet, whether this be a vertical or a horizontal layer, .are fixed to a corresponding manifold which will be either vertical or horizontal, respectively.

This design of heat exchanger is basically suited to provide a tube bank in which the tubes are arranged inline, that is to say, there are rows of tubes in line with one another when one views the bank either from above or from the side. This arrangement does not give optimum efficiency of heat transfer when the flow of the fluid through the shell is across the tubes of the bank rather than in the lengthwise direction of the tubes.

According to the invention thetubes of the tube bank are deflected from an inline arrangement by springing from near their ends adjacent tubes attached to one manifold in opposite directions so that alternate tubes attached to each header are deflected in opposite ways, and adjacent tubes of attached adjacent manifolds are sprung in the same ways. Preferably the tubes are sprung at two points so that, although they are deflected from the inline arrangement, they are substantially straight and parallel to one another over the major part of their length.

In this way the tubes of the tube bank can be simply arranged in a staggered arrangement which gives improved heat transfer efficiency as compared with an inline arrangement.

Preferably the tubes are sprung by an amount equal to one quarter of a tube spacing so that tubes of adjacent layers are staggered relatively to one another by halfa tube spacing.

If the tubes are of relatively small diameter they may be sprung by the desired amount in a relatively short distance from their ends and their connection with the manifolds. Preferably theyiare sprung by means of pairs of spacers, the first of which deflects them and is closer to the manifold and the second of which is further from the manifold and deflects them in the opposite direction so that all the tubes again extend substantially straight and parallel to one another.

A preferred heat exchanger is shown in copending U.S. application Ser. No. 807,732, filed Mar. I7, 1969, the disclosure ofwhich is incorporated herein by reference.

The invention will now be illustrated by way of example, with reference to the attached diagrammatic drawings in which:

FIG. 1 is a diagrammatic elevation showing the arrangement of tubes in a heat exchanger according to the invention;

FIG. 2 is a section taken on the line 2-2 of FIG. 1;

FIG. 3 is a section taken on the line 3-3 of FIG. 1;

FIG. 4 is a sectional elevation showing the arrangement of tubes in a heat exchanger not according to the invention; and

FIG. 5 is a sectional elevation similar to that of FIG. 4 showing the arrangement of tubes in the heat exchanger according to the invention shown in FIGS. 1 to 3.

As shown in these the heat exchanger comprises a tube bank made up of a number of tubes 101 extending between manifolds 102. The tubes of a layer or sheet are connected to an individual mainfold. As shown best in FIG. 4 this leads to an inline arrangement of'the tubes so that if fluid is passed in heat exchange with the tubes across them in the direction of the arrows 113, then the efficiency of heat exchange is not as good as it could be because preferential passages through the tube bank are left through which fluid can pass without contacting the tubes.

In accordance with the invention this is avoided by staggering the tubes so that alternate tubes connected to one manifold are bent away from one another in opposite directions. Thus as shown in FIGS. 1 and 5 the tubes I01 connected to one manifold are alternately bent so that they take up the positions shown in full lines and broken lines. This staggered arrangement prevents the formation of preferred passages through the tube bank and so improves the heat exchange efficiency by ensuring better heat exchange contact of the fluid flowing across the-tubes with the tubes.

Generally the tubes will be of very small diameter compared with their length and so they can be bent to their staggered formation in a relatively small part of their length. Preferably therefore adjacent tubes connected to a particular manifold are urged away from one another at a point A near their ends (FIG. 1) causing them to bend away from one another, and are then urged towards one another at a point B further from their ends than the point A (FIG. 1) causing them to lay parallel to one another but staggered from the inline arrangement.

Many devices may be used at the points A and B to bend the tubes. However, a preferred arrangement is to use the sinuous strips 114 and 115 shown in FIGS. 2 and 3 at the points A and B respectively. These strips 114 and 115 may be continuous or intermittent with welding at intermediate points for ease of assembly. Also they can if desired by welded to the tubes 101 to prevent sideways movement.

In'the preferred heat exchanger the tubes 101 are deflected from their straight position by a quarter of a tube spacing. In this arrangement the tubes are staggered relatively to one another by half a tube spacing.

An important advantage of the invention is its simplicity. Also the invention has advantages of manufacture since the heat exchanger is initially constructed from simple straight tubes of equal length which are bent in situ. Therefore the construction of the heat exchanger avoids the difficult and expensive steps of bending each tube individually and then accurately adjusting the length ofeach tube after bending.

A latitude of modification, change and substitution is intended in the foregoing disclosure and in some instances some feature of the invention will be employed without a corresponding use of other features. Accordingly it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.

Iclaim:

1. A heat exchanger comprising a bank of substantially straight and parallel tubes, the tubes being arranged in groups each of which constitutes one layer of tubes and the tube bank being formed by the juxtaposition of adjacent layers, a shell surrounding the tube bank, a number of inlet manifolds each joined to one layer of tubes, a number of outlet manifolds each joined to one layer of tubes, the adjacent tubes in each layer of tubes being deflected from an inline arrangement by springing at two points from near their ends so that alternate tubes in one layer are deflected in opposite ways and adjacent tubes in adjacent layers are deflected the same way and, although the tubes are deflected from an inline arrangement, they are substantially straight and parallel to one another over the major part of their length, the tubes being deflected by an amount equal to one quarter ofa tube spacing so that tubes of adjacent layers are staggered relatively to one another by half a tube spacing.

2. A heat exchanger according to claim 1 further comprising pairs of spacers which are arranged to spring the tubes, a first of said spacers deflecting said tubes and being positioned close to the inlet or outlet manifold and a second of said spacers being positioned further from the inlet or outlet manifold and deflecting said tubes in a direction opposite to the deflection produced by said first spacers so that all the tubes again extend substantially straight and parallel to one another over the major part of their length. 

1. A heat exchanger comprising a bank of substantially straight and parallel tubes, the tubes being arranged in groups each of which constitutes one layer of tubes and the tube bank being formed by the juxtaposition of adjacent layers, a shell surrounding the tube bank, a number of inlet manifolds each joined to one layer of tubes, a number of outlet manifolds each joined to one layer of tubes, the adjacent tubes in each layer of tubes being deflected from an inline arrangement by springing at two points from near their ends so that alternAte tubes in one layer are deflected in opposite ways and adjacent tubes in adjacent layers are deflected the same way and, although the tubes are deflected from an inline arrangement, they are substantially straight and parallel to one another over the major part of their length, the tubes being deflected by an amount equal to one quarter of a tube spacing so that tubes of adjacent layers are staggered relatively to one another by half a tube spacing.
 2. A heat exchanger according to claim 1 further comprising pairs of spacers which are arranged to spring the tubes, a first of said spacers deflecting said tubes and being positioned close to the inlet or outlet manifold and a second of said spacers being positioned further from the inlet or outlet manifold and deflecting said tubes in a direction opposite to the deflection produced by said first spacers so that all the tubes again extend substantially straight and parallel to one another over the major part of their length. 